DE3803581A1 - METHOD FOR PRODUCING 1,2,4-BUTANTRIOL - Google Patents

Description

1,2,4-butanetriol is a valuable intermediate with diverse Possible uses. But since only very complex and expensive Manufacturing processes for which triol has become known remain the triol the wide range of possible uses, e.g. Glycerin has found fails. It is used as a synthesis building block in drug synthesis or Manufacture of nitrates used for special explosives.

1,2,4-butanetriol is obtained by hydrating butin-2-diol-1,4 with Help from mercury catalysts. For hygienic reasons, this is Implementation unsuitable for the large-scale production of the triol. It is more advantageous if butene-2-diol-1,4-epoxide according to the information DE-AS 26 43 400 and JP-OS 59/70 632, hydrogenated to 1,2,4-butanetriol. The epoxy is made by reacting butenediol with hydrogen peroxide receive. A not very selective one Dehydration reaction on 1,3-butanediol produces 3-buten-1-ol. Out of it is obtained by subsequent hydroxylation with hydrogen peroxide on Tungsten catalyst in aqueous solution the triol.

US Pat. No. 4,410,744 proposes 2,3-epoxy-1-propanol (glycide) subject to a hydroformylation reaction and the obtained Oxo product catalytically with hydrogen or with hydrides in 1,2,4-butane convict triol. This synthesis also requires a proportionate amount expensive starting product as well as several reaction steps. It will be in the Patent noted that 1,2,4-butanetriol has so far only been used in Laboratory scale produced by hydrogenation of malic acid or its ester Has. This laboratory method is described in JACS 70, (1948), pp. 3121 to 3125 described. Then you can do it with 1.5 times the amount of one Copper chromite catalyst, based on the amount of malic acid diethyl ester to hydrogenate with 1,2 to 70% yield to 1,2,4-butanetriol. It will expressly pointed out that this high selectivity at sufficiently high reaction rate only in excess applied catalysts can be achieved. With a lower catalyst a higher reaction temperature must be maintained, which results in a corresponding reduction in selectivity.

Because malic acid is easily produced by hydrating maleic acid the task was to develop a process that it not only allows 1,2,4-butanetriol based on maleic acid Laboratory, but also to manufacture on a technical scale. It  In particular, a way had to be found, even with a low catalyst Amounts of maleic acid or its esters are economically justifiable to butanetriol hydrogenate.

It has now been found that in the preparation of 1,2,4-butanetriol by catalytic hydrogenation of malic acid esters on a copper containing catalyst at higher temperature and pressure Particularly advantageous results are obtained when adding the malic acid ester Temperatures from 130 to 190 ° C and hydrogen partial pressures from 100 to 300 bar on the fixed catalyst, largely avoided the formation of a gas phase.

The malic acid esters suitable for the hydrogenation are derived from Alcohols with 1 to 8 carbon atoms. It can be aliphatic or cycloaliphatic alcohols can be used for ester formation, such as Methanol, ethanol, propanol, butanol, 2-ethylhexanol and cyclohexanol. Alcohols with a branched carbon chain are preferred. As the best suitable starting materials have been the diisopropyl ester and in particular the diisobutyl ester proved.

The malic acid esters can be used in pure form or as dilute solutions the hydrogenation can be used. Suitable solvents are e.g. open-chain or cyclic ethers, such as diethyl ether or tetrahydrofuran, aliphatic and aromatic hydrocarbons, e.g. 5 to 10 carbon atoms may contain other solvents which are inert under the hydrogenation conditions and in particular alcohols, such alcohols being expediently used as Solvent used together with the malic acid for the Esterification were used. Are the hydrogenation solutions of Malic acid ester used, the solvent content is e.g. up to 90% by weight. Solutions with an ester content of 20 up to 80, in particular 30 to 70% by weight.

According to the hydrogenation of malic acid after so-called swamp driving style. With this method the Starting material in liquid form or the starting material solution, e.g. from bottom up or top down, on which solid in the hydrogenation reactor arranged catalyst (catalyst bed) passed, the Fixed bed catalyst essentially without a free gas space from liquid is covered.

It is hydrogenated in the presence of copper-containing catalysts for Carboxylic acid ester hydrogenation are common. These catalysts usually contain chromium as an active hydrating agent in addition to copper Metal, like the Adkins catalysts, the chromium and copper in approximately  contain equimolar amounts or those described in DE-AS 11 59 925 Catalysts in which the chromium content has been pushed back far. The In addition to copper, catalysts can also have other hydrating effects Metals such as iron, nickel, cobalt, platinum, palladium, manganese, molybdenum, Contain tungsten or vanadium, the content of these additives in The catalyst should expediently not exceed 2% by weight. The copper can on a suitable carrier, such as aluminum oxide, silica gel, pumice stone, Magnesium silicate can be applied or in a suitable manner with the carrier felled together and subsequently brought into the appropriate form. A particularly advantageous and therefore preferred catalyst, which besides Copper still contains aluminum is described in DE-OS 24 45 303.

For the fixed bed catalysis according to the bottom mode the catalysts are deformed into solids by methods known per se. Suitable forms are e.g. Bullets, tablets, rings or even simple Extrusions. These are used in suitable pressure-resistant equipment Fixed bed arranged during the hydrogenation by a closed Liquid front from the inlet and reaction product is flowed through. The Hydrogen required for the hydrogenation is at the reaction temperature and Reaction pressure dissolved in the liquid or in the form of microbubbles suspended. There is no need for an expensive one during the hydrogenation Maintain hydrogen cycle gas guidance. This creates the method according to the invention is particularly economical since a Circulating gas pump used in the ester hydrogenation known per se is not required.

It is hydrogenated at temperatures from 130 to 190 ° C, preferably at 140 to 160 ° C under a hydrogen pressure of 100 to 350, preferably 200 to 300 bar.

The liquids used for the hydrogenation should essentially be acid free. If they still contain acids, it is recommended to use them by adding an inorganic base, such as sodium hydroxide, Sodium bicarbonate, sodium carbonate, calcium hydroxide or also Neutralize potassium methylate.

By the method according to the invention is relatively low Reaction temperature a relatively high reaction rate achieved. Another advantage is that you have a high turnover a comparatively low level of by-products. That advantageous results are obtained by the process of the invention, is surprising because it was accepted doctrine for esters most conveniently use the trickle technique, as e.g. in DE-AS 11 59 925 (see column 1, lines 1 to 6 and  Column 2, lines 40 to 49). If you hydrate them Malic acid esters, however, according to the trickle method, so the Hydrogenation to 1,2,4-butanetriol only with a significantly lower one Throughput achieve that this way of working as technically usable Alternative is eliminated.

The parts mentioned in the example are parts by weight, they behave to parts by volume like kilograms to liters.

example

1000 parts by volume of the available according to Example 1 of DE-OS 24 45 303 Catalyst containing copper and aluminum are in the form of cylindrical tablets of 3 mm height and 3 mm diameter in one Shaft furnace filled. The length of the shaft furnace is related to his Diameter like 28: 1. Before the start of the hydrogenation Heating isobutanol passed through the shaft furnace and hydrogen up pressed to a pressure of 10 bar to initially the catalyst carefully reduce only in the presence of pure isobutanol. Then it will be the hydrogen pressure slowly increases from 10 to 250 bar. From 150 ° C Reduction of the catalyst, which is characterized by a noticeably exothermic Indicates reaction. As soon as this has subsided and the reduction water in the is essentially carried out, the temperature is raised to 160 ° C and a Hydrogen pressure set at 250 bar. The isobutanol feed is now by a 30% solution of diisobutyl malate in isobutanol replaced. At 160 ° C the furnace is filled with 900 parts by volume every hour Fed ester solution. At the same time there are 2000 parts by volume of the Reactor discharge in circulation with constant return. This will make the Enthalpy of reaction removed and the reactor temperature essentially guided isothermally. During the hydrogenation, the furnace will be hourly 50 normal volumes of hydrogen are removed. You get hourly 900 parts of reaction discharge with the following composition:

86% by weight of isobutanol
2% by weight 1,4-butanediol
0.2% by weight of diisobutyl succinate
0.5% by weight 1,2-butanediol
1% by weight of diisobutyl malate
0.2% by weight of monoisobutyl malic acid
10 wt% 1,2,4-butanetriol

Fractional distillation gives the mixture in vacuo colorless 1,2,4-butanetriol of 99.8% purity.  

The triol is obtained with a yield of 60% of theory. Th., But with about doubled throughput if a 60 wt .-% for the hydrogenation Solution of diisobutyl malate in isobutanol used and the Performed hydrogenation at 170 ° C.

Claims (2)

1. A process for the preparation of 1,2,4-butanetriol by catalytic hydrogenation of malic acid esters on a copper-containing catalyst at elevated temperature and pressure, characterized in that the malic acid esters at temperatures from 130 to 190 ° C and hydrogen partial pressures from 100 to 300 bar past the fixed catalyst, largely avoiding the formation of a gas phase. 2. The method according to claim 1, characterized in that as Malic acid ester the diisopropyl ester or the diisobutyl ester used.